Recently, a variety of types of optical discs have been proposed as a recording medium that can be removed from a recording apparatus. These recordable optical discs have been proposed as a large capacity medium of several GBs and are thought to be promising as a medium for recording AV (audio visual) signals. Among the sources (supply sources) of digital AV signals, recorded on the recordable optical disc, there are, for example, CS digital satellite broadcast and BS digital broadcast. For future use, ground wave television broadcast of the digital system has also been proposed.
It should be noted that digital video signals, furnished from these sources, are routinely compressed in accordance with MPEG (Moving picture Experts Group) 2 system. For the recording apparatus, a recording rate proper to the apparatus is set. If digital video signals, derived from the digital broadcast, are recorded by a conventional video storage medium for domestic use, in accordance with an analog recording system, digital video signals are first decoded and subsequently band-limited for recording. Alternatively, with the digital recording system, exemplified first of all by MPEG1 video, MPEG2 video or DV system, the digital video signals are once decoded and subsequently re-encoded in accordance with the recording rate and encoding system proper to the apparatus for recording.
However, with such recording method, in which the bitstream furnished is once decoded and subsequently bandwidth-limited or re-encoded prior to recording, the picture quality is necessarily deteriorated. If, in recording compressed digital signals, the transmission rate for input digital signals is not higher than the recording rate of the recording and/or reproducing apparatus, such a method in which the bitstream furnished is directly recorded without decoding or re-encoding suffers from picture quality deterioration to the least extent. However, if the transmission rate of the compressed digital signals exceeds the recording rate of the disc as the recording medium, it is truly necessary to first decode the digital signals in the recording and/or reproducing apparatus and to re-encode the digital signals for recording so that the transmission rate will be not higher than the upper limit of the recording rate of the disc.
If the signals being transmitted in accordance with a variable rate system in which the bitrate of the input digital signals is increased or decreased with time, the capacity of the recording medium can be exploited less wastefully in such a disc recording system in which data can be stored once in a buffer and recorded in a burst-like fashion than with a recording system in which the rotary head is of a fixed rpm and hence the recording rate is a fixed recording rate.
In the near future when digital broadcast becomes the mainstream, it may be premeditated that there is a positive demand for such a recording and/or reproducing apparatus in which aired signals are recorded in the state of digital signals, without decoding or re-encoding, as in the case of a data streamer, and in which a disc is used as a recording medium.
Meanwhile, in recording an AV stream data on a recording medium by the above-described recording apparatus, an AV stream data may be analyzed to enable fast replay to detect the position of an I-picture to effect recording such as to enable accessing an I-picture. Alternatively, the AV stream may be directly recorded without analysis.
In such case, the conventional practice has been to provide respective dedicated application programs by means of which the AV stream is recorded on the recording medium as AV streams of different formats. The result is that development of an application program tends to be costly and time-consuming. In the AV streams recorded in respective application programs, the format is different, from one AV stream to another, with the result that the respective AV streams cannot be reproduced on the same apparatus because of lack of compatibility.
In addition, the conventional recording apparatus has a drawback that audio data, for example, are difficult to post-record.